This invention relates to a purified protein which functions as a mycobacterial receptor for fibronectin and to improved methods for the treatment of superficial urinary tract tumors.
The efficacy of adjuvant intravesical Bacillus Calmette-Guerin (BCG) for superficial bladder cancer was first reported by Morales and associates in 1976. Morales et al., J. Urol. 116: 180-183, 1976. Although the efficacy of BCG is clearly established, the mechanisms by which BCG mediates antitumor activity are not clearly understood.
Previous studies have shown that BCG attachment to fibronectin (FN) in the bladder lumen is required for the development of an antitumor response. Kavoussi et al., J. Clin. Invest. 85: 62-67, 1990. Inhibition of FN-mediated BCG attachment was shown in these studies to inhibit immunization, the expression of delayed type hypersensitivity and antitumor activity. Further studies showed that BCG-mediated antitumor activity was dependent on T lymphocytes. Ratliff et al., J. Urol. 137: 155-158, 1986. These studies led to the hypothesis that BCG-induced antitumor activity is comprised of a series of event which begin with attachment and progress through immune activation and culminate in tumor destruction.
Recent studies demonstrated that BCG attach to and are ingested by bladder epithelial cells. Becich et al., J. Urol. 145: 1316-1324, 1991. Although the role of cellular attachment and ingestion by epithelial cells in BCG-mediated antitumor activity has not been clearly established, this observation suggests that BCG interaction with tumor cells may be associated with immune modulation. There remains a need to more clearly define the interaction of transitional epithelial carcinoma cells with BCG.
In addition, in vitro characterization studies have demonstrated that BCG, as well as other mycobacteria tested, attached to FN-coated surfaces but not surfaces coated with laminin, fibrinogen, or Type IV collagen. Ratliff et al., Cancer Res. 47: 1762-1766, 1987 and Ratliff et al., J. Gen. Microbiol. 134: 1307-1313, 1988. The BCG/FN interaction was saturable, FN specific, essentially irreversible and inhibited by pretreatment with protease suggesting the presence of specific bacterial receptor. Aslanzadeh et al., J. Gen. Microbiol. 135: 2735-2741, 1989. Further studies showed that BCG attachment to FN was inhibited by components contained in the supernatants of proliferating BCG suggesting that the receptor(s) were released into the supernatant. Abou-Zeid et al., Infect. and Immun., 56: 3046-3051, 1988 and Ratliff et al., J. Gen. Microbiol, 134: 1307-1313, 1988. This hypothesis was supported by several independent observations including: (a) radiolabelled proteins from BCG supernatants attached to FN-coated surfaces, Abou-Zeid et al., supra; (b) the supernatant component(s) inhibited the attachment of BCG to FN, Ratliff et al., J. Gan. Microbiol., supra; (c) the inhibitory activity was removed from affinity chromatograph on FN-Sepharose, Ratliff et al., J. Gen. Microbiol., supra; and (d) proteins from BCG supernatants separated on sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and blotted to nitrocellulose bound FN, Abou-Zeid et al, supra.
There has been a need to characterize and evaluate the components involved in BCG attachment and ingestion or internalization by the bladder tumor cell line and to develop improved delivery systems for the treatment of superficial urinary tract tumors.